1. Field of the Invention
The present invention relates to a direct smelting plant for producing molten metal from a metalliferous feed material such as ores, partly reduced ores and metal-containing waste streams.
2. Description of Related Art
A known direct smelting process, which relies principally on a molten bath as a reaction medium, and is generally referred to as the HIsmelt process, is described in International Application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application in the context of producing molten iron includes:                (a) forming a bath of molten iron and slag in a vessel;        (b) injecting into the bath:                    (i) a metalliferous feed material, typically iron oxides; and            (ii) a solid carbonaceous material, typically coal, which acts as a reductant of the iron oxides and a source of energy; and                        (c) smelting metalliferous feed material to iron in the metal layer.        
The term “smelting” is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce molten metal.
The HIsmelt process also includes pist-combusting reaction gases, such as CO and H2 released from the bath, in the space above the bath with oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also includes forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable ass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process the metalliferous feed material and solid carbonaceous material is injected into the molten bath through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into a lower region of the vessel so as to deliver at least part of the solids material into the metal layer in the bottom of the vessel. To promote the post-combustion of reaction gases in the upper part of the vessel, a blast of hot air, which may be oxygen enriched, is injected into an upper region of the vessel through a downwardly extending hot air injection lance. Offgases resulting from the post-combustion of reaction gases in the vessel are taken away from the upper part of the vessel through an offgas duct. The vessel includes refractory-lined water cooled panels in the side wall and the roof of the vessel, and water is circulated continuously through the panels in a continuous circuit.
The HIsmelt process enables large quantities of molten metal, such as molten iron, to be produced by direct smelting in a single compact vessel. However, in order to achieve this it is necessary to transport large quantities of hot gases to and from the vessel, transport large quantities of the metalliferous feed material, such as iron-containing feed materials, to the vessel, transport large quantities of the molten metal product and slag produced in the process away from the vessel, and circulate large quantities of water through the water cooled panels—all within a relatively confined area. These functions must continue throughout a smelting operation—which extends over a long period. It is also necessary to provide access and handling facilities to enable access to the vessel and lifting of equipment between smelting operations.
U.S. Pat. No. 6,399,016 in the name of Burrow and assigned to the applicant discloses a very effective arrangement of a direct smelting plant that separates the equipment required for the various functions into distinct zones that are disposed about the vessel so as to minimise the potential for interference between the various functions and to maximise safety of the smelting operations.
Specifically, the Burrow US patent discloses a direct smelting plant that includes a fixed smelting vessel, a solid feed means, an oxygen-containing gas injection means, an oxygen-containing gas delivery duct means, an offgas duct means, a metal tapping system, and a slag tapping system. The plant is characterised by locating:                (a) the oxygen-containing delivery duct means and the offgas duct means in a first of three discrete zones spaced circumferentially about the vessel;        (b) the metal tapping system in a second of the three zones; and        (c) the slag tapping system in the third of the three zones.        
The disclosure in the Burrow US patent is incorporated herein by cross-reference.
The above discussion of the Burrow US patent is not to be taken as an admission that the disclosure in the patent is part of the common general knowledge.
The present invention further addresses the issue of providing a plant layout that enables the required functions of supplying large quantities of feed materials (solid and gas) to a compact vessel, removing large quantities of products of the process (metal, slag, and offgas) from the vessel, circulating large quantities of water through the water cooled panels of the vessel, permitting access to the vessel for re-lining and other maintenance purposes, and permitting access to the vessel for lifting equipment.
The present invention provides a plurality of platforms around the vessel and locates equipment for carrying out the various functions (such as metal tapping systems, slag tapping systems, access doors, etc) in relation to these platforms so that so that the equipment is accessible by plant operators on the platforms.